Civil Engineering Reference
In-Depth Information
Wasted Space.
Improvements in general wealth and associated living standards resulted in most dwell-
ings being constructed with two full-height storeys or even more, with the roof void being
left for storage only. The use of interlocking pantiles and slates reduced roof pitches even
further and thousands of houses were built during the industrial revolution with a roof
space open from one end of the terrace to the other. Clearly in such situations access to the
roof space was not desirable between dwellings for security reasons and the roof space
was completely lost to the occupants. A typical terrace roof construction, albeit with a di-
viding or 'party' wall, is shown in Fig. 1.10.
After the Second World War, there was a great need to economise on the use of all impor-
ted building materials including timber, the main material used for the construction of
dwelling roofs. TDA (Timber Development Association) prepared a range of standard
roof truss designs which dramatically changed the domestic roof structure of the day, cre-
ating at one and the same time a structurally sound roof construction and one which used
significantly less timber than pre-war constructions.
Chapter 4 deals with this type of construction, Figs 4.4 and 4.5 depicting the trussed roof
structure.
The Final Blow
During the 1960s the trussed rafter began to be used for domestic roof construction; today
it accounts for 95% of all dwelling roofs in this country. The trussed rafter placed at 600
mm centres reduces the usable roof void to a relatively small triangle in the centre of the
roof (see Fig. 1.12). This area also has to accommodate the water tank platform, thus fur-
ther restricting access to the roof void. The trussed rafter was certainly not designed to
carry any floor loading, but adequately accommodates light domestic storage. Coupled
with the introduction of the trussed rafter roof was the further development of double in-
terlocking concrete tiles, which allowed even lower pitches down to 15ยบ in some cases.
Clearly, on relatively small spans the resulting roof void scarcely gave sufficient room to
allow the installation and servicing of the cold water storage tank, let alone provide useful
storage. Fortunately, current architectural style is towards a steeper pitched roof but only
for aesthetic reasons, few housing developers taking advantage of the void so created to
form additional habitable accommodation.
